Particularly high output powers in conjunction with good beam quality can be achieved with so-called tapered diode lasers. These semiconductor lasers have an amplifying region which widens laterally in the emission direction, and can generate, for example, infrared laser radiation with a radiation power in the watts range. A laser of this type is described, for example, in Sumpf et al., “735-nm Tapered Diode Lasers with Nearly Diffraction-Limited Beam Properties at P=2 W”, Electron. Lett. 38, 2002, pp. 183-184.
Tapered diode lasers normally comprise an injector region and a trapezoidal region adjacent thereto. The trapezoidal region has a trapezoidally expanding cross section proceeding from the injector region. If a light wave propagates in the direction of the trapezoidal region proceeding from the injector region, then the wavefront is diffracted at the transition between these two regions. The wave is amplified in the trapezoidal region. Reflective boundary surfaces of the tapered diode laser arrangement can be coated in such a way that the resulting feedback suffices to initiate the self-oscillation.
A facet provided at the injector region can have a more highly reflective coating, while an exit facet at an end of the expanding region which is remote from the injector region has a lower reflectivity.
Tapered diode lasers are distinguished in particular by the comparatively high optical output power in conjunction with good beam quality.